Wheelchair, particularly electric wheelchair

ABSTRACT

Disclosed is a wheelchair, particularly an electric wheelchair, comprising a frame ( 20 ), at least one steerable wheel ( 3 ), two non-steerable wheels ( 5 ) which are connected to the frame ( 20 ) at a wheelbase (R), and a seat ( 10 ) that is fastened to the frame ( 20 ) and is provided with a back rest ( 8 ). The inventive wheelchair is characterized by the fact that the wheelbase (R) is adjustable.

The invention relates to a wheelchair, particularly an electricwheelchair, having a frame, at least one wheel which is mountedrotatably about an axis of rotation and is steerable, and twonon-steerable wheels which are connected in relation to each other tothe frame in a wheelbase R, and having a seat which is fastened to theframe and has a backrest.

In the case of these known wheelchairs, the frame has a fixed size whichdetermines the size of the wheelchair. The spectrum of body sizes of thepossible wheelchair users means that it is not possible to adapt thecenter of gravity of the body in respect of the optimum pivotal point ofthe wheelchair. This means that a very large person sits too far to therear, with the result that the overall center of gravity is shifted toofar to the rear, and a very small person sits too far forward, with anoverall center of gravity shifted further forward. The differentposition of the overall centers of gravity results in the load beingdistributed unfavorably to the driving or steering wheels, thus limitingthe driving performance.

In order to shift the center of gravity, seat systems which can bedisplaced in the longitudinal direction on fixing elements on the frameare known. However, a system of this type increases the overall lengthof the wheelchair, thus restricting its ability to turn.

U.S. Pat. No. 4,405,142 discloses a wheelchair in which the steerablefront wheels are fastened to a separate front frame. The end tubes ofthe front frame can be pushed into tubes of the rear frame. Holes whichare spaced apart in parallel in the front frame and rear frame and intowhich bolts can be inserted make it possible to adjust the length of thewheelchair and therefore the wheelbase. This configuration makes itimpossible to optimally align the center of gravity because thewheelbase can only be adjusted in stages which are predetermined by thehole spacing. In order for the two frame parts to be connected in acompletely fixed manner and for it not to be possible for the frontframe to shake, there should not be any play between the hole and bolt.The connection therefore has to take place via fixing pins, which isvery complicated structurally. Severe jarrings are caused by thewheelchair traveling on public paths and roads, and traveling over curbsand the like. In order for the fixing connection between the tubes notto be knocked out, there have to be high wall thicknesses and the fixingpin has to have a large diameter, which then means that the tubediameter has to be correspondingly large. The security of sufficientstability is then inevitably paid for by a high frame weight.

Taking this problem as the starting point, the wheelchair explained atthe beginning is to be improved, with the above disadvantages beingavoided, to the effect that it can be adapted in largely optimum fashionto the user's size.

To solve the problem, a wheelchair of the generic type is distinguishedin that the wheelbase can be adjusted in an infinitely variable manner,and in that the distance of the axis of rotation of the steerable wheeland the frame can be adjusted.

The infinitely variable adjustability of the wheelbase permits an exactadaptation to the user's height. The steering wheel rotates optimallyabout the fork axle if the latter is situated perpendicularly withrespect to the driving plane. If the distance between the axis ofrotation and the frame can be adjusted, a change in the angle of thefork during the telescoping process can be compensated for, with theresult that the perpendicular pivot axis is always maintained.

In order to adjust the wheelbase, the frame is of telescopic design. Tothis end, preferably at least two concentrically arranged tubes areprovided, the relative position of which tubes in relation to oneanother can be fixed by at least one clamping element.

In particular, it is advantageous if the position of the tubes can befixed by three clamping elements which can be fastened in relation toone another.

The at least one steerable wheel is preferably mounted in a fork in amanner such that it can rotate about a horizontal axis of rotation, andthe fork is connected to one of the tubes in a manner such that it canpivot about a vertical axis.

In order to adjust the distance between the axis of rotation of thewheel and the frame, a plurality of vertically spaced holes ispreferably provided at the lower end of the fork, into which holes thewheel axle can alternatively be fitted. As an alternative, the fasteningof the wheel axle may also be realized via an elongated slot withclamping, as is known, for example, in the case of racing bicycles.

The position of the seat in relation to the frame can preferably also beadjusted, so that the seat can be optimally adapted in the horizontalplane to the change in the frame length. It can thus be ensured that thedistance of the footrests from the steered wheels is sufficiently largethat the latter can pivot freely.

The frame is essentially formed by two tubes which run parallel to eachother, are each arranged concentrically and are connected to each othervia a welded transverse strut and a battery tray screwed on from below.This configuration makes it possible for the rear tubes which are largerin diameter (main tubes) to be rigid and the tubes which are smaller indiameter and are connected in each case to a steered wheel to then forma telescopic front frame.

An exemplary embodiment of the invention will be explained in moredetail below with the aid of a drawing, in which:

FIG. 1 shows a side view of a wheelchair;

FIG. 2 shows the enlarged detail according to the viewing arrow II fromFIG. 1;

FIG. 3 shows the section along the line III-III from FIG. 2.

The electric wheelchair, the drive units of which are not illustratedspecifically here, has a frame 20 on which two steerable front wheels 3and two driving wheels 5 are arranged spaced apart from one another inthe wheelbase R. The frame 20 is essentially formed by tubes 11, 7 whichare arranged on both sides, run concentrically and are connected to eachother via the seat 10 and adaptation tabs 6, 16.

The front frame, which is formed by the tubes 11, is telescopic. To thisend, the tube 11 corresponds in the outside diameter to the insidediameter of the tube 7 and is pushed into the latter.

In a recess, three clamping elements 13, 14, 15 are provided one behindanother in the longitudinal direction in the tube 11. The two outerclamping elements 13, 15 are beveled at their inner ends. The centralclamping element 14 is beveled congruently at its two ends to theclamping elements 13, 15. The three clamping elements 13, 14, 15 are ineach case provided with a passage hole (not referred to specificallyhere). The passage hole of the inner clamping element 15 is providedwith an internal thread 17. The passage hole of the outer clampingelement 13 has a stepped hole 13′ which serves to receive a screw head(not illustrated specifically here). The clamping elements 13, 14, 15are fastened to one another via a screw (not illustrated) which isscrewed into the thread 17, the bevels causing the central clampingelement 14 to be pressed radially outward against the inner wall of theouter tube 7, so that the relative position of the inner tube 11 inrelation to the outer tube 7 can be fixed in an infinitely variablemanner. It is also conceivable for the tubes 7, 11 to be able to betelescoped in a stepped manner by, for example, holes which are spacedapart in parallel being provided in the walls, being brought to overlapand then a bolt being inserted through them. Other fixing means are alsoconceivable.

The outer tubes 7 are connected to one another via a welded transversestrut—not illustrated here—and a battery tray which is screwed on frombelow.

The driving wheels 5 are connected to the rigid tubes 7 via rearadaptation tabs 6. A steering wheel mount 1 is provided at the free endsof the inner tubes 11 and accommodates a fork 2, which can pivot aboutthe vertical axis H and in which the steering wheels 3 are fastenedmounted in a manner such that they can rotate about an axis of rotationD. The telescopability of the frame 20 enables the wheelbase R to beadjusted in an infinitely variable manner.

As FIG. 1 shows, the tubes 7, 11 are inclined with respect to thecontact area of the wheels 3, 5. If the tubes 7, 11 are telescoped, theangle of the vertical axis H of the fork 2 changes in relation to theperpendicular. The pivotability of the steering wheels 3 is optimum ifthe vertical axis H coincides as far as possible with the perpendicular.In order to compensate for the change in the angle during thetelescoping of the frame 20, a plurality of vertically spaced holes 4are provided at the lower end of the fork 2, into which holes the wheelaxle can alternatively be inserted, so that the distance A between theaxis of rotation D of the steering wheel 3 and the frame 20 can beadjusted. Instead of a plurality of holes 4, an elongated hole, in whichthe axle of the steering wheel 3 can be clamped, could also be providedin the fork 2.

In order to adapt the seat 10 to the individually adjusted wheelbase R,a plurality of horizontally spaced holes 9, 9′ is provided in the seat10, via which the seat can be fastened to the adaptation tabs 6, 16.

The backrest 8 of the seat 10 can be adjusted in angle electrically. AsFIG. 3 shows, the tubes 7, 11 are of oval design in cross section, thusresulting in great stability.

LIST OF REFERENCE NUMBERS

-   1—Steering wheel mount-   2—Fork-   3—Front wheel/steering wheel-   4—Hole-   5—Rear wheel/driving wheel-   6—Adaptation tab-   7—Tube-   8—Backrest-   9—Hole-   9′—Hole-   10—Seat-   11—Tube-   12—Tab-   13—Clamping element-   13′—Recessed hole-   14—Clamping element-   15—Clamping element-   16—Adaptation tab-   17—Thread-   20—Frame-   A—Distance-   D—Axis of rotation-   H—Vertical axis-   R—Wheelbase

1. A wheelchair, particularly an electric wheelchair, comprising: aframe including at least one inclined telescopically adjustable member,said inclined telescopically adjustable member inclined upwards in afront-to-back direction, at least one steerable wheel mounted to saidinclined telescopically adjustable member by a mounting means, said atleast one steerable wheel being rotatable about a horizontal axis ofrotation, said mounting means being pivotal about a pivot axis extendingrelative to said at least one inclined telescopically adjustable member,at least one non-steerable adjustable wheel that is connected to theframe at a wheelbase location, and a seat which is fastened to theframe, wherein the seat has a backrest, wherein the mounting means hasmeans for adjusting the distance between the horizontal axis of rotationand the frame at a respective telescoping of said inclinedtelescopically adjustable member, to adjust the pivot axis to besubstantially vertical.
 2. The wheelchair of claim 1, wherein the seatis fastened to the frame by a means for adjusting the position of theseat in relation to the frame.
 3. The wheelchair of claim 1, wherein theinclined adjustable member comprises an outer tube having an innerperimeter shape and an inner tube having an outer perimeter shape scaledwith respect to with the inner perimeter shape of the outer tube suchthat the inner tube is telescopically movable with respect to the outertube, said outer tube, and wherein the inner tube is selectively fixedto the outer tube by at least one clamping element.
 4. The wheelchair ofclaim 3, wherein the at least one steerable wheel is mounted in a forkin a manner to rotate about the horizontal axis of rotation, wherein thefork is connected to one of the inner and outer tubes, and wherein thefork pivots about the pivot axis.
 5. The wheelchair of claim 4, whereinthe means for adjusting the distance between the horizontal axis ofrotation and the frame includes a plurality of vertically spaced holesprovided at a lower end of the fork.
 6. The wheelchair of claim 3,wherein said clamping element is positioned between said inner tube andsaid outer tube, and wherein said clamping element comprises a firstmember having tapered ends, and a second and third member each have atapered end engaging a tapered end of said first member, and means forcompressing said second and third members against said first member. 7.The wheelchair of claim 6, wherein said first, second and third membersare tubes.